The present invention relates to a hand tool. More particularly this invention concerns such a tool having a handle portion, a blade, and a system for releasably securing the blade to the handle so it can be exchanged for an identical replacement blade or for another blade serving a different purpose.
A hand tool is known, for instance from German patent 240,786 of C. Wusthof, which has a blade having a longitudinally inwardly projecting tang that fits in a socket or seat in a separate handle part. A pivotal lever on the handle can swing between a flush holding position in which a transverse retaining formation on the lever engages a transverse retaining formation on the tang and locks the blade to the handle and an extended freeing position disengaging these retaining formations and permitting the blade to be pulled out of the handle and replaced by another blade. A clip on the handle can retain the lever in the flush holding position to maintain the blade locked to the handle, and a spring normally urges the retaining lever into the extended freeing position. Thus one knife blade can be exchanged for another, or for a saw blade or specialty blade. The blade, when installed, is very solidly mounted to the handle so it can be used for cutting, prying, or twisting like with a one-piece tool.
A disadvantage of this system is that both releasing and securing a blade are two-step operations. To release the blade the clip must be opened and the lever flipped back; to secure the blade the lever must be swung forward and the clip closed. If the clip is accidentally bumped and opened, the lever will swing out under spring force and the blade will separate from the handle. Another disadvantage is that the contact area between the retaining formation is limited so that it can loosen when worn, letting the blade move relative to the handle when locked in place.
It is therefore an object of the present invention to provide an improved hand tool with a changeable blade.
Another object is the provision of such an improved hand tool with a changeable blade which overcomes the above-given disadvantages, that is which is easy to use and which ensures a very solid anchoring of the blade in the handle.
A hand tool has according to the invention an elongated blade having a longitudinally inwardly projecting tang having a longitudinal back edge formed with a plurality of transversely directed teeth, a longitudinal front edge, and an elastically transversely deflectable retaining formation. A handle forms a longitudinally open seat having one longitudinally extending side wall. A retaining lever has an edge formed with teeth and an elastically transversely deflectable retaining formation. The lever is displaceable between a closed holding position with the lever teeth meshing with the blade teeth and pressing the blade against the seat wall and the formation transversely engaging and bearing elastically against the blade retaining formation, and an open freeing position with the lever teeth out of mesh with the blade teeth and the formation out of engagement with the blade retaining formation.
Thus this tool is quite simple. The interaction of the retaining formations hold the lever releasably in the closed holding position so that no biasing spring or clip are needed. Changing blades is simply a question of pulling out the retaining lever to free the blade and pushing it back in after the replacement blade is in place. There is no clip to actuate.
According to the invention the retaining formation of the blade is at an inner end of the tang. In addition the tang and blade lie in a longitudinal plane and the retaining formation of the blade is bent at an acute angle out of the plane.
The retaining formations in accordance with the invention have flat faces flatly engaging each other in the closed holding position. In this manner enough friction is present to ensure adequate holding of the lever in the closed position. To maximize this effect the tang tapers away from the blade. Furthermore the teeth of the retaining lever fit complementarily in the closed holding position with the teeth of the tang.
The handle according to the invention has a transversely extending structure spaced from the side wall. The tang is snugly engaged between the side wall and the structure when inserted in the seat. This structure is a crosswise pin.
The blade in accordance with the invention has a transversely projecting finger shield. This finger shield, the blade, and the tang are unitarily formed of metal.